It floats more or less in the fluid, which of course is the spirit of turpentine. The trick, with this preparation, after having put some of the solid and fluid substance together on a plate, is to pour upon it concentrated nitric acid, or a mixture of eight or ten parts of nitric acid, and two of sulphuric acid; inflammation ensues. It is no other in fact than accension of the oil of turpentine; the addition of the spermaceti is altogether secondary, and its effect, if any, must retard instead of promoting the combustion of the turpentine. The art of making this preparation is in rendering the essential oil solid and transparent, without altering its inflammable properties.

There is another trick performed, by burning a thread, to which an ear-ring is tied, and which, notwithstanding the thread is reduced to a cinder, still holds the ring. This is what the French call the Bague suspendue aux cendres d'un fil. The string is first prepared by soaking it for 24 hours, in a solution of common salt, and drying it; then tying it to a ring, and setting it on fire, avoiding any vibration or oscillation of the string. It is obvious that the salt serves to render the cinder cohesive.

We have an account in Maundrel's Travels from Aleppo to Jerusalem, of the office of the Holy Fire. The ceremony is kept up by the Greeks and Armenians, from a persuasion that every Easter eve, a miraculous flame descends from heaven into the holy sepulchre, and lights all the lamps and candles, as the sacrifice was consumed at the prayers of Elijah.

"On our approaching the holy sepulchre," says Maundrel, "we found it crowded with a numerous and distracted mob, who made a hideous clamour; but with some difficulty pressing through the crowd, we got up in the gallery next to the Latin convent, where we could have a view of all that passed. The people began, by running with all their might, round the holy sepulchre, crying out 'huia,' which signifies, 'This is he,' or, 'This is it.' After this, they began to perform many antic tricks: sometimes they dragged one another along the floor round the sepulchre; sometimes marched round with a man upright upon another's shoulders; at others, took men with their heels upwards, and hurried them about with such indecency, as to expose their nudities; and sometimes they tumbled round the sepulchre like tumblers on a stage. In a word, nothing can be imagined more rude and extravagant than what was acted upon this occasion.

"This frantic humour continued from twelve till four, and then the Greeks first set out in a procession round the sepulchre, followed by the Armenians, and marched three times round it with their standards, streamers, crucifixes, and embroidered habits; and towards the end of the procession, a pidgeon came fluttering into the cupola over the sepulchre, at which the people redoubled their shouts and clamours, when the Latins told the English gentlemen, that this bird was let fly by the Greeks, to deceive the people with a belief that it was a visible descent of the Holy Ghost. The procession being over, the suffragan of the Greek patriarch, and the principal Armenian bishop, approached the door of the sepulchre, cut the string with which it was fastened, and breaking the seal, entered, shutting the door after them, all the candles and lamps within having been before extinguished in the presence of the Turks. As the accomplishment of the miracle drew near, the exclamations were redoubled, and the people pressed with such violence towards the door, that the Turks could not keep them off with the severest blows. This pressing forward was occasioned by the desire to light their candles at the holy flame as soon as it was brought out of the sepulchre. The two miracle-mongers had not been above a minute in the sepulchre, when the glimmering of the holy fire was seen through some chinks in the door, which made the mob as mad as any in bedlam; then presently came out the priests, with blazing torches in their hands, which they held up at the door of the sepulchre, while the people thronged with extraordinary zeal to obtain a part of the first and purest flame, though the Turks laid on with their clubs without mercy. Those who got the fire immediately applied it to their beards, faces, and bosoms, pretending that it would not burn like an earthly flame; but none of them would endure the experiment long enough to make good that pretension. However, so many tapers were presently lighted, that the whole church seemed in a blaze, and this illumination concluded the ceremony."

Maundrel afterwards observes, that the Latins take great pains to expose this ceremony as a shameful imposition, and a scandal to the Christian Religion: but the Greeks and Armenians, lay such stress upon it, that they make the pilgrimages chiefly on this account; and their priests have acted the cheat so long, that they are forced now to stand to it, for fear of endangering the apostacy of the people. They entertain many absurd ideas respecting the miraculous power of the holy fire. Even the melted wax of the candle, which had been lighted by it, is covered over with linen, and designed for winding-sheets; "for they imagine," says Maundrel, "that if they are buried in a shroud, smutted with this celestial fire, it will secure them from the flames of hell!"

Before concluding this article, we shall mention a subject highly interesting in optics, which, in some of its forms, was employed by the old magicians; we mean the phantasmagoria. The exhibitions of this kind, when first got up, drew the attention of Europeans, and particularly the French, who greatly improved the apparatus and machinery, and varied the forms and appearances. The principles of the phantasmagoria are described in every work on Natural Philosophy, which treats of optics. The Dictionnaire de l'Industrie, Encyclopedie Méthodique, Biot's Traité de Physique, in French and in English, the different treatises on philosophy and optics, particularly Dr. Smith's, the Cyclopedias, &c. contain either a description, or the principles of it. The third volume of Biot, especially, is full on the subject of optics. With regard, however, to the narrative and explanation of the appearance of the phantoms, and other figures, a subject which immediately concerns us, the account given by Mr. Nicholson, (Journal of Natural Philosophy, Chymistry, and the Arts, vol. i, p. 147.) is the most interesting. Connected with this optical illusion, is the imitation of lightning and thunder, which, from the account, appears also to have been performed.

The phantasmagoria may be considered nothing more than an application of the magic lantern, the invention of which is attributed to Roger Bacon, who was a contemporary with Vitellio, a native of Poland, who published a treatise on optics, in 1270. John Babtista Porta, of Naples, who discovered the camera obscura, having formed a society of ingenious persons at Naples, which he called the Academy of Secrets, wrote the Magia Naturalis, containing his account of this instrument, and, it is said, the first hint of the magic lantern. Kircher, it is known, received his first information of the magic lantern from this book, and afterwards improved it.

Adams (Lectures on Natural and Experimental Philosophy, vol. ii, p. 232. Appendix by the English editor) very justly observes, that persons, unacquainted with the principles of optics, have been surprised at the great illusion of their sight, by an artificial construction of many optical instruments, exhibited by showmen and others: such, for instance, as the optical and dioptrical paradox; the endless gallery; the animated balls by simple reflection; phantoms; causing the appearance of a flower from its ashes; the optical perspective box, and the cylindrical mirror: to which we may add, the enchanted bottle; the enchanted palace; the magic lantern; the magician's mirror; the perspective mirror; the camera obscura; distorting and oracular mirror; the diagonal opera glass, &c. &c.; all which may be seen in Smith's School of Arts.

We may also remark, that optical exhibitions sometimes accompany those of fire, when performed on a small scale. In the phantasmagoria, for instance, whether before, or at the time the exhibition commences, as well as after, thunder and lightning, if well imitated, produces a good effect.

The mechanism of the phantasmagoria is concealed from the spectators, who have only before their eyes a screen of gauze or gummed muslin posited vertically, which serves as the ground of a picture, where the images are depicted by reason of the transparency. The apartment is deprived of all light, except that which proceeds from an apparatus hid behind the screen. At the moment when the operation commences, a spectre appears (as a skeleton, the head of a celebrated person, &c.), at first extremely small, but which afterwards increases rapidly, and thus seems to advance at a great rate towards the spectators. And when the scene passes before them in a room representing a cave hung with black, a solemn silence being occasionally interrupted by mournful sounds from an appropriate musical instrument, it is not easy for an observer to defend himself from the impression of terror, at the sight of an object, in itself formed to produce the illusion, and which finds in the imagination a place already prepared for the reception of phantoms.

The instrument placed behind the gauze screen is in fact a peculiar construction of the magic lantern: only in the former, it is necessary that the lenses should run over a much greater space, and that the instrument may be susceptible of approaching to, and receding from, the frame of gauze, in such manner, that each luminous pencil may be depicted there in a single point. The general construction is this: In a square box, a lamp is placed, the luminous rays proceeding from which, are reflected by a conical mirror, towards an orifice made in the box. At this orifice is placed a tube, blackened within, and composed of several tubes which slide one into another, like those of a pocket telescope. This tube is furnished with two bi-convex lenses of about five inches diameter; one of these is fixed, the other is at the outer extremity of the tube, and is separated from the former in proportion as the tube is lengthened by the aid of a hooked lever situated along the tube, between the lamp and the lenses. A groove is properly adapted to the tube, destined to receive transparent figures; lastly, the box rests upon a table moveable on four wheels, that slide in two channels perpendicularly to the frame on which the images are depicted. It is manifest, that we may augment or diminish the dimensions of the images, and consequently make the spectre appear more or less near to the spectator, by separating farther, or by bringing nearer together, the two lenses; but then the focus of the diverging rays, which proceed from the same point of the transparent body, will be no longer upon the screen; we must, therefore, cause the machine so to recede or approach, that the two motions, being duly combined, the image may be distinctly formed.

These phantasmagoria are furnished with a great number of transparencies, in each of which, several changes may be made by slackening their springs. Thus we may change at every instant, the form, the magnitude, and the distance of the spectres, as they appear to the spectator.

What has been said hitherto, relates only to the images of transparent figures. To obtain those of opaque bodies, first place the gauze and box, at the distance of about six feet one from the other, and adapt to the orifice of the box, an apparatus of two tubes furnished with two bi-convex lenses. An opaque body, such, for example, as a medal, or a picture, is attached to a little support, posited in the middle of the box; the lamp with its supply of air, situated in one of the foremost corners of the box, illuminates that object, and the reflected rays, crossing the lenses, proceed till they trace the image upon the gauze, with an amplification which is in the ratio of the distances.

If the image be not distinct, we must infer that it is not at the focus; but it may be adjusted in three different ways; 1. By moving the box to or from the gauze; 2. By moving the object nearer to, or farther from, the lenses within the box; 3. By slowly moving the tubes, to cause a variation in the distance between the lenses.—See Haüy's Philosophy, translated by Gregory, vol. ii, p. 390.

Mr. Nicholson, however, witnessed an exhibition of the phantasmagoria at the London Lyceum by Philipstal, who took out a patent for his improvements in the apparatus and machinery. He observes, that the novelty consists in placing the lantern on the opposite side of the screen which receives the images, instead of on the same side as the spectator, and suffering no light to appear but what passes through, and tends to form those images. His sliders are therefore perfectly opaque, except that portion upon which the transparent figures are drawn, and the exhibition is thus conducted.

All the lights of the small theatre of exhibition were removed, except one hanging lamp, which could be drawn up, so that its flame should be perfectly enveloped in a cylindrical chimney, or opaque shade. In this gloomy and wavering light, the curtain was drawn up, and presented to the spectator a cave or place exhibiting skeletons, and other figures or terror, in relief, and painted on the sides or walls. After a short interval, the lamp was drawn up, and the audience were in total darkness, succeeded by thunder and lightning; which last appearance was formed by the magic lantern upon a thin cloth or screen, let down after the disappearance of the light, and consequently unknown to most of the spectators. These appearances were followed by figures of departed men, ghosts, skeletons, transmutations, &c. produced on the screen by the magic lantern on the other side, and moving their eyes, mouth, &c. by the well known contrivance of two or more sliders. The transformations are effected by moving the adjusting tube of the lantern out of focus, and changing the slider during the moment of the confused appearance.

It must be again remarked, that these figures appear without any surrounding circle of illumination, and that the spectators, having no previous view or knowledge of the screen, nor any visible object of comparison, are each left to imagine the distance according to their respective fancy. After a very short time of exhibiting the first figure, it was seen to contract gradually in all its dimensions, until it became extremely small, and then vanished. This effect, as may easily be imagined, is produced by bringing the lantern nearer and nearer the screen, taking care at the same time to preserve the distinctness, and at last closing the aperture altogether: and the process being (except as to brightness) exactly the same as happens when visible objects become more remote, the mind is irresistibly led to consider the figures, as if they were receding to an immense distance.

Several figures of celebrated men were thus exhibited with some transformations; such as the head of Dr. Franklin being converted into a skull, and these were succeeded by phantoms, skeletons, and various terrific figures, which instead of seeming to recede and then vanish, were (by enlargement) made suddenly to advance; to the surprise and astonishment of the audience, and then disappear by seeming to sink into the ground.

This part of the exhibition, which by the agitation of the spectators appeared to be much the most impressive, had less effect with me than the receding of the figures; doubtless because it was more easy for me to imagine the screen to be withdrawn than brought forward. But among the young people who were with me, the judgments were various. Some thought they could have touched the figures, others had a different notion of their distance, and a few apprehended that they had not advanced beyond the first row of the audience.

The whole, as well as certain mechanical inventions, were managed with dexterity and address. The lightning, being produced by the camera, was tame, and had not the brisk transient appearance of the lightning at the theatres, which is produced by rosin, or lycopodium powder, thrown through a light, which in Mr. P's utter darkness might easily have been concealed in a kind of dark lantern.

A plate of thin sheet iron, such as German stoves are made of, is an excellent instrument for producing the noise of thunder. It may be three or four feet long, and the usual width. When this plate is held between the finger and thumb by one corner, and suffered to hang at liberty, if the hand be then moved or shaken horizontally, so as to agitate the corner at right angles to the surface, a great variety of sounds will be produced; from the low rumbling swell of distant thunder, to the succession of loud explosive bursts of thunder from elevated clouds. This simple instrument is very manageable, so that the operator soon feels his power of producing whatever character of sound he may desire; and notwithstanding this description may seem extravagant, whoever tries it for the first time will be surprised at the resemblance. If the plate be too small, the sound will be short, acute, and metallic.

We may remark also, that the magic lantern, by new contrived sliders and machinery, may be applied to important uses, by employing it with such figures as will explain the general principles of optics, astronomy, botany, &c.

The experiment mentioned by Ferguson, with a concave mirror, reflecting into the air the appearance of fire, &c. into a focal point, (founded on a general principle of concave reflectors,) is productive of many agreeable deceptions, and which exhibited with art and an air of mystery, has been very successfully employed.

The phantasmascope of Walker is similar to the phantasmagoria. It is an optical machine, which presents a door that opens itself. The apparatus is so contrived, that, on opening the door, a phantom makes its appearance, having all the colours of a picture, which approaches the spectator. Various figures may be accurately represented.

We will not enlarge on this subject, although many other instances of tricks, performed by means of fire, &c. might be noticed. We will merely remark:

1. For the performance of these exhibitions, the ancient, as well as the modern jugglers, of all descriptions, employed, and were acquainted with sundry mixtures, and compositions, by the use of which, they deceived the people; and some pretended to possess supernatural agencies. Of these compositions, with many of which we are unacquainted, we have enumerated some, and their effects. That of producing a callosity of the skin, &c. by means of acids, is an example.

2. That they possessed, as a trade or profession, the arts of deception. Not only by the use of chemical preparations, but by other means, they pretended to work miracles in the dark ages of science. However degraded these persons may seem, they yield in vice to another class, who practised the art of poisoning, and who kept it so profound a secret, that few then understood the effect of the now common, vegetable, and mineral poisons. Who could have been more infamous than the celebrated female poisoner, Tophania?